Artificial photosynthesis can store solar energy and reduce CO2 into fuels to potentially alleviate global warming and energy crisis. Compared to gas products, it remains a grand challenge to tune the product distribution of artificial photosynthesis to liquid fuels, such as CH3OH, that are suitable for storage and transport. This paper describes the introduction of metallic Cu nanoparticles (NPs) on Cu2O films to change the product distribution from gas products on bare Cu2O to predominant CH3OH via CO2 reduction in aqueous solutions. The specifically designed Cu/Cu2O interfaces could balance the binding strengths of H* and CO* intermediates, which plays critical roles in CH3OH production. With TiO2 model photoanode to construct a photoelectrochemical cell, Cu/Cu2O dark cathode exhibited a Faradaic efficiency up to 53.6% for CH3OH production. This work demonstrates the feasibility and mechanism of interface engineering to enhance the CH3OH production from CO2 reduction in aqueous electrolytes.